Check for continuous binary tree in java

Java program for Check for continuous binary tree. Here problem description and other solutions.

/* 
  Java program for
  Check if binary tree is continuous tree
  Using recursion
*/
// Binary Tree Node
class TreeNode
{
    public int data;
    public TreeNode left;
    public TreeNode right;
    public TreeNode(int data)
    {
        // Set node value
        this.data = data;
        this.left = null;
        this.right = null;
    }
}
public class BinaryTree
{
    public TreeNode root;
    public BinaryTree()
    {
        // Set initial tree root
        this.root = null;
    }
    public int absValue(int num)
    {
        if (num < 0)
        {
            return -num;
        }
        return num;
    }
    // Check tree is continuous or not
    public boolean isContinuous(TreeNode node)
    {
        if (node != null)
        {
            if ((node.left != null  && absValue(node.data - node.left.data) != 1) || 
                (node.right != null && absValue(node.data - node.right.data) != 1))
            {
                // Case
                // When fail continuous tree rule
                return false;
            }
            if (isContinuous(node.left) && isContinuous(node.right))
            {
                return true;
            }
            // When node value is not satisfied continuous tree properties
            return false;
        }
        return true;
    }
    public static void main(String[] args)
    {
        // Create new tree
        BinaryTree tree = new BinaryTree();
        /*  
           Binary Tree
           ------------
               5
             /   \
            4     4
           /     /  \
          3     5    3
           \
            2
        */
        // Add tree node
        tree.root = new TreeNode(5);
        tree.root.left = new TreeNode(4);
        tree.root.right = new TreeNode(4);
        tree.root.left.left = new TreeNode(3);
        tree.root.right.right = new TreeNode(3);
        tree.root.right.left = new TreeNode(5);
        tree.root.left.left.right = new TreeNode(2);
        if (tree.isContinuous(tree.root) == true)
        {
            System.out.println("Continuous Tree ");
        }
        else
        {
            System.out.println("Not Continuous Tree ");
        }
      	// Case 2
        /* 
               5
             /   \
            4     4
           /     /  \
          3     5    3
           \
            1  <--- change value
        */
      	tree.root.left.left.right.data = 1;
        if (tree.isContinuous(tree.root) == true)
        {
            System.out.println("Continuous Tree ");
        }
        else
        {
            System.out.println("Not Continuous Tree ");
        }
    }
}

Output

Continuous Tree
Not Continuous Tree